This document relates generally to semiconductor devices, and more specifically to trench power field effect transistors (FET).
Manufacturers of integrated circuits are continually seeking ways to reduce manufacturing costs and thereby increase profits. One way in which manufacturers of integrated circuits can reduce manufacturing costs is by increasing the number of integrated circuits they form on each semiconductor wafer. An increased number of integrated circuits per semiconductor wafer can be accomplished by reducing the distance or “pitch” between various circuit features, elements, and components. Unfortunately, when circuit features, elements, and components are placed closer together they may begin to unintentionally interact or sometimes even overlap other features, elements, and components of the circuit. These unintended interactions may interfere with the operation and characteristics of the integrated circuit. For example, in a trench power MOSFET device, a reduction in pitch could be obtained by reducing the distance between the source-body contact and the trenched gate. However, by bringing the source-body contact closer to the trenched gate, the body contact region, which may be doped at a higher dopant concentration than the body region, may begin to interfere with, or even overlap, the device's inversion channel. This interference can affect the threshold voltage and other characteristics of the device.
Accordingly, it is desirable to be able to reduce the pitch of trench power FET devices in integrated circuits without having the features, elements or components of the integrated circuit unintentionally interact or overlap with each other.
For simplicity and clarity of illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote generally the same elements. Additionally, descriptions and details of well-known steps and elements may be omitted for simplicity of the description. As used herein current-carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor, an emitter or a collector of a bipolar transistor, or a cathode or anode of a diode, and a gate electrode means an element of the device that controls current through the device such as a gate of a MOS transistor.
Although the devices are explained herein as certain N-channel devices, a person of ordinary skill in the art understands that P-channel devices and complementary devices are also possible in accordance with the present description. For clarity of the drawings, some doped regions of device structures may be illustrated as having generally straight-line edges and precise angular corners. However, those skilled in the art understand that due to the diffusion and activation of dopants, the edges of doped regions are generally not straight lines and the corners are not precise angles.
Furthermore, the term “major surface” when used in conjunction with a semiconductor region or substrate means the surface of the semiconductor region or substrate that forms an interface with another material, such as a dielectric, an insulator, a conductor, or a polycrystalline semiconductor. The major surface can have a topography that changes in the x, y and z directions.
In addition, structures of the present description may embody either a cellular base design (where the body regions are a plurality of distinct and separate cellular or stripe regions) or a single base design (in which the body region is a single region formed in an elongated pattern, typically in a serpentine pattern or a central portion with connected appendages). However, one embodiment of the present description will be described as a cellular base design throughout the description for ease of understanding. It should be understood that the present disclosure encompass both a cellular base design and a single base design.